K1SHEKY tSULLtlLM: VUL. 81, l^U. '1 



dispersal from its usual host. It may be an example of 

 a parasite species utilizing an alternate host in the ab- 

 sence of its preferred host. Finally, U. reductus, the 

 most specialized species of Unicolax, has been found 

 only on a highly specialized host, Katsuwonus. This 

 indicates that Katsuwonus evolved from the Euthyn- 

 nus stock, and U. reductus evolved from the ancestor 

 of U. mycterobius. 

 It should be noted that, in each of the three tribes, 

 Unicolax was not found in the most specialized scom- 

 brid genus. In Thunnus this may be the result of com- 

 petition resulting from heavy infestations of the 

 monogenetic trematode, Nasicola klawei (Stunkard), 

 in the nasal sinuses of the host fish. There is no 

 evidence, however, that parasite competition is a fac- 

 tor in Acanthocybium, Gymnosarda, and Allothun- 

 nus. It may be that as each of the tribes evolve, the 

 most specialized members lose parasites. This con- 

 cept is consistent with other data presented else- 

 where in this paper (see Scomberomorus infestation 

 data in Table 6 and Sarda parasite discussions). 



COMPARISON OF COPEPOD 



PARASITES IN 



SCOMBRIDAE AND BELONIDAE 



After completing the analysis of the parasitic cope- 

 pods of the Scombridae, it seemed instructive to 

 make comparisons with those of the Belonidae, the 

 only other family of fishes that has been studied in a 

 similar manner (Cressey and Collette 1970). The 

 Scombridae (48 species) is a larger family than the 

 Belonidae (32 species). All scombrids are marine 

 species, although several enter estuaries and only 

 Scomberomorus sinensis is found far up the Mekong 

 River. Four genera of Belonidae (Belonion, Potomor- 



rhaphis,Pseudotylosurus, andXenentodon) plus three 

 species of Strongylura are restricted to freshwater, 

 and populations of several other species of Stron- 

 gylura invade freshwater long enough to acquire 

 freshwater parasites. Thus, parasites of the family 

 Ergasilidae (nine species) must be omitted in any 

 comparisons because they are restricted to hosts in 

 freshwater. Several other families of copepods can- 

 not be used because their habitat does not occur in 

 the host group. Species of Shiinoidae live inside the 

 nasal cavities of their host, attached to the lamellae of 

 the nasal rosettes. Belonidae have an open nasal pit 

 with no place for a Shiinoa to attach. Scombrid 

 species breathe largely by ram-jet ventilation of the 

 gills and so have small oral valves in the upper and 

 lower jaws, apparently too small to house the caligid 

 copepod Caligodes which was found on seven species 

 of Belonidae. Several species of the caligid genus 

 Caligus were found on needlefishes but all in small 

 numbers, partially because Cressey and Collette's 

 study used mostly preserved specimens that were 

 prone to lose parasites like Caligus, which are mostly 

 external. 



Two ecological habitats, parasitized by three fami- 

 lies of copepods in the two families of fishes, seem 

 comparable — gills and oropharyngeal cavity. Bomolo- 

 chid copepods are found in the oropharyngeal cavity 

 of both host families (and also in the nasal cavities of 

 the Scombridae). Species of the closely related 

 families Lernanthropidae and Pseudocycnidae at- 

 tach permanently to the gills of belonids and scom- 

 brids, respectively (Table 10). 



Comparison of the parasitic copepod fauna of the 

 most speciose genera of each family, Strongylura and 

 Scomberomorus, reveals some interesting dis- 

 tributional patterns. Bomolochus bellones, the com- 

 mon bomolochid of Strongylura, extends from the 



Table 10. — Comparison of parasitic copepod fauna on gills (Lernanthropidae 

 and Pseudocycnidae) and oropharyngeal cavities (Bomolochidae) in genera from 

 the Belonidae (Strongylura) and Scombridae (Scomberomorus). 



Strongylura 



5 species 

 Bomolochus bellones (5/5) 

 Bomolochus sinensis (1/5} 

 Nothobomolochus digitatus ( 1 /5) 

 Lernanthropus be/ones (3/5) 

 Lernanthropus tylosun (5/5) 



S senegalensis 

 Bomolochus bellones 



3 species 

 Bomolochus bellones (3/3) 

 Lernanthropus be/ones (3/3) 

 Lernanthropus tylosun (2/3) 



2 species 

 Bomolochus constrictus (2/2) 

 Bomolochus ensiculus (2/2) 

 Lernanthropus belones (2/2) 

 Lernanthropus tylosun (1/2) 



Indo-West Pacific 



Eastern Atlantic 



Western Atlantic 



Eastern Pacific 



Scomberomorus 



1 species 

 Unicolax ciliatus (9/10) 

 Pseudocycnoides armatus (8/10) 

 Pseudocycnoides scomberomon (1/10) 



S. tritor 



Unicolax ciliatus 



4 species 

 Holobomolochus divancatus (3/4) 

 Hofobomolochus asperatus (1/4) 

 Pseudocycnoides buccata (4/4) 



2 species 

 Holobomolochus nudiusculus (2/2) 

 Pseudocycnoides buccata (2/2) 



260 



